Re: [Gumstix-users] Re: Find LCD timing for the ALPS on gumstix.org

hi Ohm,
the photos you posted look quite good in that you have real data going
to the screen, colors are good, pixels are ordered and text can be made
out and horiz and vert syncing seems ok ie things appear in the right
place on screen.
I suspect the problem with the 'faded' look could be a polarity issue.
Look at the three polarity settings pixclockpol (reg LCCR3_PCP) hsync
(LCCR3_HSP) and vsync (LCCR3_VSP). Each of these can be one or zero. I
would try all eight combinations from 0,0,0 .... to 1,1,1 see what
changes and what looks best. (Of course I have to add the disclaimer -
if the magic smoke gets out it's not my fault!) Maybe you've tried this
already.
If you hit the right combination and the text looks crisp it may throw
the syncing right out, then you have to tweak hsynclen (LCCR1_HSW)
vsynclen(LCCR1_VSW) left (LCCR1_BLW) and right (LCCR1_ELW) to straighten
things up
According to the Intel docs upper (LCCR2_BFW) and lower (LCCR2_EFW)
should be set to zero for a passive screen and vsynclen(LCCR1_VSW)
should be increased to allow wait states at the start of frame but YMMV
Also you can send text to the screen like this:
echo "Hello World" > /dev/tty0
there's actually a lot you can do with this redirection method, you can
send the text output of any program to the LCD by appending ' > /dev/tty0'
It would be cool if what was typed at the serial console appeared
directly on the text console, any linux console gurus know how to do
this ? Is it something trivial or does it require extensive kernel
hacking :) ;) in all my searching of console-HOWTOS and docs I havn't
come across an answer to this one.
Another question to the gurus, should I be using /dev/tty1 /dev/console
or /dev/tty0 in the above examples (or just whatever works) ?
cheers, Michael
ohm unmongkolthavong wrote:
>Hi Mr. Sutherland,
>
>The cable is about 4.5" long. the connectors are the
>back of the LCD screen and a custom daughtboard with a
>24-pin wire connector.
>
>I checked the connections and they are all sound and
>solid.
>
>I can get it to a point where i still lose one side of
>the screen due to bad timing, but the text is now
>readable. I wrote a little script that changed the
>LCCR3_PCD from 0 to 255, hoping that somewhere along
>script, the screen would be readable. However, the
>loss of the screen (graying of a the screen) goes from
>the left to the right as the numbers increase.
>
>-Can anyone suggest another path to take towards
>finding the bug-free display?
>-Is there a way to change the actual pixel clock using
>pxaregs? I was wondering if there was another register
>that handled the clock. I'm reading the PXA
>developer's manual, and as mentioned before, it really
>DOES make your head spin. Hopefully, though, i'll find
>some info on the pixel clock.
>
>While we're here, I noticed that text that i type does
>NOT show up on the screen. It only prints out the
>boot-up messages (the dmesg stuff) and then stops
>there. I will do a search around the archives to find
>some info, but if anyone could point me in the right
>direction, I would totally appreciate it.
>
>Thanks for everyone's help! I hope this newb can be
>like the LCD masters here one day.
>Ohm
>
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